In assembly plants or storage depots, newly assembled vehicles are usually driven under their own power between several locations all within a short distance of each other. As a result, the vehicle engine runs for very short intervals with a fuel rich mixture at temperatures well below its normal operating temperature (50-70% of normal operating temperature, i.e., 350.degree.-400.degree. C. at plug tip).
In spark ignition internal combustion engines, such operation frequently leads to fouling of the engine spark plugs by carbon and unburnt fuel deposition on electrodes as result of imperfect combustion. This is to be distinguished from gum deposits which form as fuel residue and cannot be burnt away at normal operating temperatures. The fouling provides difficulties in moving vehicles within the plant or depot. Additionally, when the vehicle is delivered to the retailer, it is often necessary to fit a new set of spark plugs to the engine before the vehicle is sold to the customer. This adds to the final cost of the vehicle.
This invention relates to methods of operating newly assembled motor vehicles in vehicle assembly plants or storage depots.